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Fix native frame unwind in syscall on arm64 for VS4Mac crash report. #63598

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Merged
mikem8361 merged 3 commits into from
Jan 13, 2022
Merged

Fix native frame unwind in syscall on arm64 for VS4Mac crash report. #63598

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Fix native frame unwind in syscall on arm64 for VS4Mac crash report.
Jan 6, 2022
b7a8bd4
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Jan 11, 2022
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Jan 12, 2022
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Mike McLaughlin committed Jan 11, 2022
commit b7a8bd4b6d7d234e151296d91bec9c4eaf87625d
27 changes: 20 additions & 7 deletions src/coreclr/pal/src/exception/remote-unwind.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#include <mach-o/nlist.h>
#include <mach-o/dyld_images.h>
#include "compact_unwind_encoding.h"
#define MACOS_ARM64_POINTER_AUTH_MASK 0x7fffffffffffull
#endif

// Sub-headers included from the libunwind.h contain an empty struct
Expand Down Expand Up @@ -1423,6 +1424,8 @@ StepWithCompactNoEncoding(const libunwindInfo* info)
#if defined(TARGET_ARM64)

#define ARM64_SYSCALL_OPCODE 0xd4001001
#define ARM64_BL_OPCODE_MASK 0xec000000
#define ARM64_BL_OPCODE 0x84000000

static bool
StepWithCompactNoEncoding(const libunwindInfo* info)
Expand Down Expand Up @@ -1519,7 +1522,7 @@ StepWithCompactEncodingArm64(const libunwindInfo* info, compact_unwind_encoding_
return false;
}
// Strip pointer authentication bits
context->Lr &= 0x7fffffffffffull;
context->Lr &= MACOS_ARM64_POINTER_AUTH_MASK;
}
else
{
Expand Down Expand Up @@ -1742,7 +1745,7 @@ static void UnwindContextToContext(unw_cursor_t *cursor, CONTEXT *winContext)
// Strip pointer authentication bits which seem to be leaking out of libunwind
// Seems like ptrauth_strip() / __builtin_ptrauth_strip() should work, but currently
// errors with "this target does not support pointer authentication"
winContext->Pc = winContext->Pc & 0x7fffffffffffull;
winContext->Pc = winContext->Pc & MACOS_ARM64_POINTER_AUTH_MASK;
#endif // __APPLE__
TRACE("sp %p pc %p lr %p fp %p\n", winContext->Sp, winContext->Pc, winContext->Lr, winContext->Fp);
#elif defined(TARGET_S390X)
Expand Down Expand Up @@ -2155,12 +2158,22 @@ PAL_VirtualUnwindOutOfProc(CONTEXT *context, KNONVOLATILE_CONTEXT_POINTERS *cont
result = GetProcInfo(context->Pc, &procInfo, &info, &step, false);
if (result && step)
{
// If the PC is at the start of the function and the unwind encoding is frameless, back up PC by 1 to the previous
// function and get the unwind info for that function. This for functions that have been optimized to tail call.
if ((context->Pc == procInfo.start_ip) && (procInfo.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_FRAMELESS)
// If the PC is at the start of the function, the previous instruction is BL and the unwind encoding is frameless
// with nothing on stack (0x02000000), back up PC by 1 to the previous function and get the unwind info for that
// function.
if ((context->Pc == procInfo.start_ip) && (procInfo.format & (UNWIND_ARM64_MODE_MASK | UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK)) == UNWIND_ARM64_MODE_FRAMELESS)
{
TRACE("Getting unwind info for PC - 1\n");
result = GetProcInfo(context->Pc - 1, &procInfo, &info, &step, false);
uint32_t opcode;
unw_word_t addr = context->Pc - sizeof(opcode);
if (ReadValue32(&info, &addr, &opcode))
{
// Is the previous instruction a BL opcode?
if ((opcode & ARM64_BL_OPCODE_MASK) == ARM64_BL_OPCODE)
{
TRACE("Getting unwind info for PC - 1\n");
result = GetProcInfo(context->Pc - 1, &procInfo, &info, &step, false);
}
}
}
}
#else
Expand Down